Error -200077, USB 6008, deterministic application

[Delta D]

Hi

I am acquiring and generating analog signals using a USB 6008 device to achieve feedback control. I am using a simulation loop to generate the controller's output, thus need to synchronize the input/output signals with the software calculations. I have the following questions:

1. When I use a sample clock for the analog output I get an error (-200077). What is the cause of this error and are there any solutions?

2. What values of step size and timing period (simulation loop parameters) should I use to ensure determinism?

Any comments are appreciated.

Thanks.

[Christian Mergl]

What did the error tell you under the "Possible Reasons" Section?

It should point you to the parameter which seems to be out of range and also give you the minimal and maximal values of the property you want to set.

And please post DAQ Questions at the DAQ Forum the next time.

Thanks,

Christian

[Dennis_Knutson · Accepted solution]

The 6008 does not have an output clock. It is software timed and therefore not deterministic.

[SimonH]

Delta D,

Error -200077 means that the operation you are trying to perform or the values you selected are not supported on the device you are using. Specifically in your case the USB-6008 does not support hardware-timed analog output (Hardware timing == sample clock).  You can get around the error by specifying software timing and controlling the update speed in software using a timed loop (this will be less accurate but is supported by your hardware).  The USB-6210 is probably the closest device that does offer hardware-timed AO if you need the speed/accuracy of hardware timing.

Using USB and a desktop OS like Windows you cannot really ensure determinism since neither your hardware bus nor OS guarantee a deterministic response -- this is where LabVIEW Real-Time and PCI/PXI/CompactRIO based hardware comes in.  But assuming you aren't trying to get too crazy with your update speed and being late every now and then isn't going to be the end of the world then you can definitely do control in almost real-time* with your setup (* although not technically real-time since you don't have bounded jitter, your USB-bus could be busy, and Windows could start updating/defragging/virus-scanning causing you to be late updating an output).

Best of luck,

Simon

[SimonH]

Dennis, you beat me every time.

That's what I get for my longwinded responses 

[JÞB]

Simon.

the 6210 does not support hardware timing and has 0 (zero) AO.  the 625x series would be a better fit. 

[Delta D]

Thank you all for your responses! They were very helpful:)

D.